Everything you always wanted to know about fish farming but were afraid to ask

Aquaculture is booming: As of 2012, we produce more farmed fish than beef worldwide, some 66 million tons. And while fish farming has a bad reputation, the mangrove-plowing, antibiotic-dosing, overcrowded and under-regulated shrimp- and salmon-farms of the 1980s are — like Members Only jackets and crimped hair — largely relics of those times, with a few heinous exceptions. The New Aquaculture(TM) is sleek and clean, with always-advancing science and technology on hand to help producers keep an eye on sustainability, as well as the bottom line.

And it’s working: According to a report from U.N.’s Food and Agriculture Organization, aquaculture will grow by 50 percent over the next 15 years, while fisheries will probably only grow by a couple billion tons. That means, by 2030, we will farm as many fish as we catch — to the tune of 90 million tons.

When we started thinking about meat over here at Grist — I mean really thinking — we pretty much expected to stay on land. After all, most of us take a pretty Three Musketeers approach to the subject, with beef, chicken, and pork the center and sum of all things meat (turkey being the D’Artagnan of this metaphor). But we know that conventionally raised meat can be pretty fraught — and, more generally, that eating animals is not always the most efficient way to get calories into people. And sensible or not, all signs suggest we’re only going to be eating more meat as the global population gets bigger and richer. So it’s worth looking at better alternatives — and that means looking underwater.

Can farmed fish be good?

Graham Young, director of the publicly funded Western Regional Aquaculture Center and a professor of fishery sciences at the University of Washington, thinks aquaculture just has a PR problem — and he should know, since, in some ways, he is one of aquaculture’s PR people. But having spent a lot of time talking to fishermen and fisheries scientists, I am more and more convinced that there’s something to Young and other’s can-do attitude: Aquaculture’s potential for good really is greater than its record for harm. Even more strikingly, every expert I have spoken to agrees, however begrudgingly, that it will be a necessary part of our future food scene. So let’s get it right.

But first we have to get over a couple of hurdles. Which brings us back to Young’s PR problem: We usually talk about farming fish as an alternative to capturing wild fish — but that’s comparing the proverbial apple to the idiomatic orange. Yes, well-managed wild-capture fisheries are about as low-impact as food gets, as vocal proponents like Paul Greenberg and Andy Sharpless have argued. But no matter how green our fisheries are, there will always be a limit to how much we can catch. If we take any more than that, we’ll outpace the environment’s ability to keep churning out fish.

And where, exactly, is that limit? We’re pretty much already there, says Young. There aren’t many unexploited fisheries left in the world’s heavily fished oceans, and it’s unlikely we’ll stumble upon a new one. Meanwhile, we’re running out of farmland above water — so if we’re going to produce more meat, and do it better, we are going to need new ideas.

Can farmed fish be green?

Fish farming, unlike fishing, is a food production system. It may not be as romantic as scooping a live fish from the briny deep, but it is a hell of a lot more efficient. Fish farming, done well, could potentially provide a reliable amount of protein for a fraction of the energy costs and labor that go into hunting them down at sea. “Any food production system has impacts,” says Young. The real question is not “fishing or farming?” but “farming fish or farming any other animal?” In other words: Which food production system has the fewest impacts?

And when you do that math, aquaculture is pretty promising — especially when it centers on species that are already low on the food chain. For one thing, shellfish farmers don’t have to feed their flock, which gather all the nutrients they need for free, and clean the water as they do so. Some especially promising aquaculture projects pair shellfish with other fish — this shrimp farm, for example, that grows clams in cages suspended in their shrimp ponds, or this experimental polyculture farm off the coast of British Columbia that ekes free harvests of mussels, oysters, scallops, and sugar kelp just from the waste of their highly prized black cod.

There are also plenty of finfish that make fairly successful vegetarians, which means their impact is lighter than most. Tilapia and catfish, for example, are especially good at turning low-cost plant-based feed into high-quality protein. And unlike cows and chickens, which are also arguably vegetarian, fish don’t need to burn calories to stay warm or stay upright, so more of their feed ends up as flesh. For commercially raised fish, the average feed-to-weight ratio is around 1 to 1 while other livestock can take as many as eight pounds of feed to get that single pound of flesh.

Can farmed fish be cool?

But how many discerning gourmets, out for dinner, would choose the tilapia over the steak? While shellfish and bottom-feeders are important pieces of the food security puzzle, aquaculture is also going to have to churn out something a little more prestigious if it’s going to take a slice of the meatloaf that the world’s growing middle class demands. Salmon, tuna, trout — these are the closest gill-breathers get to the cultural behemoth that is the ribeye steak. And while they’re challenging to grow, these species are becoming more and more common, as researchers and entrepreneurs crack the codes — genetic and otherwise — that allow us to grow salmon indoors, and tuna in open-ocean ranches.

Farmed salmon, once the super villain spread at your bagel brunch, has been raking in the “Most Improved” awards left and right. The first farmed salmon was even certified sustainable last year, according to a set of standards established by the Aquaculture Stewardship Council. What changed?

Most fish, especially those top-of-the-food-chain carnivores like salmon and trout, need certain omega-3 compounds in their food in order to grow — and it turns out the easiest way to get these nutrients has traditionally been to turn low-value forage fish from the wild into food for farmed fish. So fish meal and fish oil have long been the fuel behind the aquaculture boom. That — combined with the fact that many wild forage fish populations are currently crashing — has led to claims the we are fishing out the bottom levels of the ocean food chains, to the detriment of all.

But, in fact, the amount of fish meal that we use has stayed relatively constant since 2000, even as the percentage that goes toward aquaculture continues to grow. That means we’re feeding less fish meal to livestock like pigs and chickens, says Young — which was standard practice for a long time, back when the stinky stuff was considered a low-value nutritional supplement. Those days are over! Along with European vacations andcomfortable retirement, fish meal is now a relative luxury, thanks to the advent of aquaculture.

In the end, Young says, like a lot of aquaculture’s challenges, “it’s going to come down to economics.” Yes, fish meal and fish oil are expensive — they’re limited resources and laborious to produce, but that means that producers will have to figure out how to use them as efficiently as possible. Even the farmed species that require on the omega-3s in fish oil can be fed a diet that largely consists of other proteins, like soy- or algae-based feeds, with just enough oil to make everything run smoothly.

And researchers are constantly looking to dig up new alternatives to both fish meal and oil — things that might be even lighter on the land, like insects, or genetically modified flax, or yeast-grown omega-3 oils that can be churned out in fermenting vats with almost no waste at all.

Can farmed fish be clean?

And while we’re talking waste: Fish farms have a bad reputation for flooding the waters around their pens with the stuff — professionals call it “effluent,” but we’ll go pre-adolescent and just say “poo.” The nitrogen-heavy pile-up can lead algal blooms and subsequent microbe busts that suck the oxygen out of the water. (That’s called a “dead zone,” which sounds like either zombies or collapsed ecosystems. Either way, we’re scared.) Large and crowded populations of farmed fish, out at sea, can also be a reservoir for sea lice and other disease that may in turn infect local species.

But these problems are mostly a matter of location, location, location, Young says. Fish farms that are located in areas with good water circulation and robust local ecosystems may have barely any effect on local wildlife at all. Anchored open-ocean ranches may be one version of this, with the first floating farms popping up in Hawaii and elsewhere in the last few years. But it doesn’t have to be that extreme — and a little ocean can go a long way, Young says.

“In the Norwegian salmon industry, which is probably the first or second producer of Atlantic salmon, if you lined the cages up side by side, you would occupy the main runway on the Stockholm airport,” Young says. That’s not a lot of space — about 60 acres, if you trust my math — to grow a lot of food — about a million tons of salmon.

And then there are on-land fish farms, which exist in closed systems that draw water in and flush waste out. In theory, these systems could be tuned to recirculate almost all of their water. In practice, that kind of energy-intensive operation is rarely economically viable, at least not yet.

“Right now, the technology is still promising,” Young says, but of the examples of scaled-up recirculating aquaculture projects, he says, “I can’t think of many who survived more than a few years.”

Can farmed fish be better?

Perhaps the most audacious and simplest advance in aquaculture has been a matter of DNA. And no, we’re not talking genetically engineered fish like the much-contested AquaBounty salmon, which relies on a spliced gene to grow superlarge, superfast. We’re talking plain, old genetic selection — the oldest agricultural technology at our disposal. After all, modern cows only exist because we kept pairing off the fattest cattle and the ones that produced the most milk. The perfect farmed salmon or shrimp will come about the same way.

“We have to see aquaculture going in the way the poultry industry has gone,” Young says. (I ask if he’s aware what a contentious claim that is in my line of work, and he says he is — but that it’s still a useful measurement.) The modern chickens grown in factory farms by the millions have been genetically selected to be the perfect meat animal, capable of freakishly fast growth and tolerant of crowded conditions. Whatever you think of the morality of that, Young says, genetic selection is necessary to both the economic and environmental sustainability of aquaculture’s future, too.

In fact, it’s already getting us there. New lineages of salmon and trout can survive and thrive on ever decreasing amounts of fish oil, while still packing on the tasty, tasty pounds — and for this we can thank good ol’ unnatural selection.

And while we can’t say whether the up-and-coming world population will always choose a sustainably farmed salmon over a slab of steak, we can say that it looks more and more likely that we’ll at least be able to provide the fish to supply that appetite.

Which brings us to an oft-used metaphor for population growth and food security: Over the next 30 years, we’ve essentially invited an extra 2 to 3 billion people to the table for dinner — they didn’t ask to be there, but here they come … so we better stock up on apps and entrées. If we’re going to sate those incoming masses, we are going to have to do the most complex diner-party menu planning ever. All the choices are bad in some way or another. What’s that other saying? There’s no such thing as a free dinner, and this one is definitely going to cost us. But for a bad choice, fish looks pretty darn good.